sms: implement backspace with pad button A

blk/627

@@ -1,14 +1,15 @@
 : _cell! ( tilenum pos )
     2 * 0x7800 OR _ctl ( tilenum ) _data 1 _zero ;
+: _spc! 0 ( blank ) XYPOS @ _cell! ;
 : _lf
-    XYPOS @ 0 ( blank ) OVER _cell!
-    [ VDP_COLS LITN ] / 1+ [ VDP_ROWS LITN ] MOD
-    [ VDP_COLS LITN ] * XYPOS !
-;
+    _spc! XYPOS @ [ VDP_COLS LITN ] / 1+ [ VDP_ROWS LITN ] MOD
+    [ VDP_COLS LITN ] * XYPOS ! ;
+: _bs _spc! XYPOS @ 1-
+    [ VDP_COLS VDP_ROWS * LITN ] MOD XYPOS ! ;
 : (emit)
+    DUP 0x08 = IF DROP _bs EXIT THEN
     DUP 0x0d = IF DROP _lf EXIT THEN
     0x20 - DUP 0< IF DROP EXIT THEN
     0x5e MIN ( tilenum ) XYPOS @ _cell!
     XYPOS @ 1+ DUP [ VDP_COLS VDP_ROWS * LITN ]
-    = IF DROP 0 THEN XYPOS !
-;
+    = IF DROP 0 THEN XYPOS ! ;

blk/636

@@ -3,7 +3,7 @@
     BEGIN _updsel UNTIL
     _prevstat C@
     0x20 ( BUTC ) OVER AND NOT IF DROP _sel C@ EXIT THEN
-    0x40 ( BUTA ) AND NOT IF EXIT THEN
+    0x40 ( BUTA ) AND NOT IF 0x8 ( BS ) EXIT THEN
     ( If not BUTC or BUTA, it has to be START )
     0xd _next C! _sel C@
 ;